Conventionally, for packing of foods, pharmaceutical products, and the like, a so-called press-through pack (hereinafter PTP) packing body, in which a content is stored in a pocket produced by forming a plastic sheet and is packed by heat-sealing with an aluminum foil, to which an adhesive is applied, as a lid material, has been used. As the plastic sheet, polyvinyl chloride resin has been mainly used in terms of transparency, moldability, stiffness, and cost. However, when the content is hygroscopic, since the moisture-proof property in the polyvinyl chloride resin is poor, it has been treated by coating polyvinylidene chloride resin having excellent moisture-proof property to a polyvinyl chloride resin sheet. However, because these plastic sheets are expensive, there is a problem in terms of cost.
In recent years, in light of environmental concerns, the use of a polyvinyl chloride resin and polyvinylidene chloride resin is avoided because chlorine-including gas is generated when they are burned up. On the other hand, with the improvements in molding machines recently, a polypropylene sheet, which was conventionally hard to mold, has been focused on in terms of a moisture-proof property, low cost, and ease of treatment and has been used in several applications including PTP packing. In recent years, in order to store medications which are sensitive to moisture or in order to advance the development speed of new medications, a sheet which has a water vapor barrier property with excellent reliability has been required and a method of improving the water vapor barrier property by adding petroleum resin to polypropylene resin has been conducted. However, in the method of adding petroleum resin to polypropylene resin, although the transparency and moldability of the molded sheet are good, the water vapor barrier property is insufficient compared with a laminated sheet, in which a polyvinyl chloride resin sheet is coated with the polyvinylidene chloride resin. On the other hand, when a high-density polyethylene resin having a higher barrier property among polyolefin resins is used, although the water vapor barrier property is improved, it is required to improve a barrier property lowered due to dimensional variation after molding the sheet and transparency.